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https://issues.apache.org/jira/browse/KAFKA-10134?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17146391#comment-17146391
]
Neo Wu commented on KAFKA-10134:
--------------------------------
{code:java}
do {
client.maybeTriggerWakeup();
if (includeMetadataInTimeout) {
// try to update assignment metadata BUT do not need to block on the
timer,
// since even if we are 1) in the middle of a rebalance or 2) have
partitions
// with unknown starting positions we may still want to return some data
// as long as there are some partitions fetchable; NOTE we always use a
timer with 0ms
// to never block on completing the rebalance procedure if there's any
updateAssignmentMetadataIfNeeded(time.timer(0L));
} else {
while (!updateAssignmentMetadataIfNeeded(time.timer(Long.MAX_VALUE))) {
log.warn("Still waiting for metadata");
}
}
final Map<TopicPartition, List<ConsumerRecord<K, V>>> records =
pollForFetches(timer);
if (!records.isEmpty()) {
// before returning the fetched records, we can send off the next round
of fetches
// and avoid block waiting for their responses to enable pipelining
while the user
// is handling the fetched records.
//
// NOTE: since the consumed position has already been updated, we must
not allow
// wakeups or any other errors to be triggered prior to returning the
fetched records.
if (fetcher.sendFetches() > 0 || client.hasPendingRequests()) {
client.transmitSends();
}
return this.interceptors.onConsume(new ConsumerRecords<>(records));
}
} while (timer.notExpired());
{code}
from the current design, i guess one possible fix is to add exponentially retry
if metadata is not available and nothing returned by pollForFetches(timer), and
until timer expired
let outside application code to call consumer.poll(timeout) again
> High CPU issue during rebalance in Kafka consumer after upgrading to 2.5
> ------------------------------------------------------------------------
>
> Key: KAFKA-10134
> URL: https://issues.apache.org/jira/browse/KAFKA-10134
> Project: Kafka
> Issue Type: Bug
> Components: clients
> Affects Versions: 2.5.0
> Reporter: Sean Guo
> Priority: Blocker
> Fix For: 2.6.0, 2.5.1
>
>
> We want to utilize the new rebalance protocol to mitigate the stop-the-world
> effect during the rebalance as our tasks are long running task.
> But after the upgrade when we try to kill an instance to let rebalance happen
> when there is some load(some are long running tasks >30S) there, the CPU will
> go sky-high. It reads ~700% in our metrics so there should be several threads
> are in a tight loop. We have several consumer threads consuming from
> different partitions during the rebalance. This is reproducible in both the
> new CooperativeStickyAssignor and old eager rebalance rebalance protocol. The
> difference is that with old eager rebalance rebalance protocol used the high
> CPU usage will dropped after the rebalance done. But when using cooperative
> one, it seems the consumers threads are stuck on something and couldn't
> finish the rebalance so the high CPU usage won't drop until we stopped our
> load. Also a small load without long running task also won't cause continuous
> high CPU usage as the rebalance can finish in that case.
>
> "executor.kafka-consumer-executor-4" #124 daemon prio=5 os_prio=0
> cpu=76853.07ms elapsed=841.16s tid=0x00007fe11f044000 nid=0x1f4 runnable
> [0x00007fe119aab000]"executor.kafka-consumer-executor-4" #124 daemon prio=5
> os_prio=0 cpu=76853.07ms elapsed=841.16s tid=0x00007fe11f044000 nid=0x1f4
> runnable [0x00007fe119aab000] java.lang.Thread.State: RUNNABLE at
> org.apache.kafka.clients.consumer.internals.ConsumerCoordinator.poll(ConsumerCoordinator.java:467)
> at
> org.apache.kafka.clients.consumer.KafkaConsumer.updateAssignmentMetadataIfNeeded(KafkaConsumer.java:1275)
> at
> org.apache.kafka.clients.consumer.KafkaConsumer.poll(KafkaConsumer.java:1241)
> at
> org.apache.kafka.clients.consumer.KafkaConsumer.poll(KafkaConsumer.java:1216)
> at
>
> By debugging into the code we found it looks like the clients are in a loop
> on finding the coordinator.
> I also tried the old rebalance protocol for the new version the issue still
> exists but the CPU will be back to normal when the rebalance is done.
> Also tried the same on the 2.4.1 which seems don't have this issue. So it
> seems related something changed between 2.4.1 and 2.5.0.
>
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